In recent years, as mobile devices such as cellular phones are widely used and semiconductor devices as the main parts of personal computers and the like have higher speed and higher frequency, multilayer ceramic capacitors mounted on these electronics equipments are increasingly required to have smaller size and larger capacity.
To meet these requirements, the smaller layer thickness and the larger number of stacked layers have been attempted in dielectric layers constituting the multilayer ceramic capacitors. Therefore, crystal grains constituting the dielectric layers are required to have a high dielectric constant even if they are finely granulated and have less temperature dependence in dielectric constant. There have been developed such dielectric ceramics as disclosed in the following patent documents.
For example, Patent Document No. 1 discloses a dielectric ceramic obtained by complexing barium titanium zirconate in which a part of the titanium site within barium titanium used as a dielectric ceramic is replaced with zirconium, and bismuth sodium titanate in which the barium site is replaced with bismuth, sodium, and strontium.
Patent Document No. 2 discloses a dielectric ceramic obtained by replacing a part of the barium site within barium titanate with calcium, and replacing a part of the titanium site with zirconium, and then complexing these barium calcium titanium zirconate crystal grains having different calcium and zirconium compositions.
Patent Document No. 3 discloses a dielectric ceramic in which zirconia composition is contained in a proportion of 0.01 to 0.1 atomic percent with respect to 1 mole of a composite oxide of barium, bismuth and titanium.
Patent Document No. 4 discloses a dielectric ceramic in which 0.11 to 0.5 parts by mass of zirconia is contained with respect to 100 parts by mass of a dielectric ceramic composed of barium, titanium and a rare earth element.    Patent Document No. 1: Japanese unexamined patent publication No. 2005-22891    Patent Document No. 2: Japanese unexamined patent publication No. 2005-22890    Patent Document No. 3: Japanese unexamined patent publication No. 2003-238240    Patent Document No. 4: Japanese unexamined patent publication No. 2003-146744